There are not many liquid polymers available in the marketplace today which have good fuel, solvent, water and temperature resistance. Of those liquid polymers available in the marketplace, many are relatively expensive and the remainder have other disadvantages.
Certain prior art workers have made hydroxyl terminated polythioethers by condensing thiodiglycol in the presence of certain etherifying catalysts as, for example, shown in U.S. Pat. Nos. 3,312,743 and 3,335,189. Compounds produced by these patents give semi-crystalline waxy solids, gums or low molecular weight liquids which have limited commercial utility.
Copolymerization of thiodiglycol with dihydric alcohols is disclosed in U.S. Pat. Nos. 3,005,803; 3,985,708 and 4,093,599. Due to the fact that the hydroxyl groups on the dihydric alcohols have lower activity towards condensation than the hydroxyl groups on thiodiglycol the condensation is irregular and/or incomplete which causes the reaction product to have a very wide molecular weight distribution which is undesirable. Just as importantly, the dihydric alcohols are non-sulfur containing and therefore incorporation of these non-sulfur containing monomers in the polymer backbone significantly reduces the solvent and fuel resistance of the resulting polymer.
In addition to the foregoing deficiencies with the previously known polythioethers, the prior art polythioethers are also crystallizing products which, even if liquid or semi-liquid at ambient temperatures, when they are cooled sufficiently to solidify will not return to their previous liquid state even when the temperature is raised to ambient.